Lamda – large aperture MEMS scanner module for 3D distance measurement

At the Exhibition Micromachine/MEMS in Tokyo, the Fraunhofer Institute for Photonic Microsystems IPMS presented for the first time the prototype of a new large aperture 1D MEMS scanner module especially designed for laser radar systems. The Lamda module is a scalable MEMS scanner array composed of identical silicon mirror elements with a total scanning aperture of 2.51 x 9.51 mm² and a large optical scan range of ± 30°. The 1D MEMS scanner module comprises two separate scanning channels: a single scanning mirror of the collimated transmitted beam oscillates parallel to a scanning mirror array of the receiver optics.

Light paths of emitting and receiving optics are separated to reduce crosstalk in the final laser radar system. The receiver optics uses an array of 2 x 7 identical mirror elements resulting in a total aperture of 334 mm² and a filling factor of 80 %. All mirrors are driven electrostatic resonant at 250 Hz by means of separate in-plane comb drives with identical frequency close to the mechanical resonance for oscillation around their long symmetry axes. Thus, the transmitted beam is sent via a separate emitting master mirror of the same mechanical dimensions as one element of the mirror array. All receiving mirrors are synchronized to the master scanner by the driving control electronics to point in the same direction. Hence, the effective apertures of the receiving mirrors add up to form a sufficiently large aperture if all receiving mirrors are synchronized in phase to the emitting master mirror in order to maximize the optical signal of the detector system.

To realize the mirror synchronization, miniaturized position sensors are integrated into the Lamda module for each individual mirror element. Thus, a precise control of the mirror motion is achieved so that all receiving mirror elements can be slaved to the motion of the emission mirror. The Lamda scanner module has a total size of about 52 x 40 x 40 mm³ and provides a synchronous position signal of the actual scan angle required for the final 3D laser radar system.

Fraunhofer Institute for Photonic Microsystems IPMS
Ines Schedwill
ines.schedwill@ipms.fraunhofer.de
www.ipms.fraunhofer.de